“Richard II (1367-1400), King of England, married his second wife, Isabella of Valois (1389-1409) a few days before her 7th birthday. They spent time together but there is no record of consummation.”
H. Eugene Lehman writes of Isabella of Valois in his book Lives of England’s Reigning and Consort Queens:
‘His new child-bride was treated as an adopted daughter, in which the consummation of marriage was never contemplated. The tender and mutual relationship that developed between Richard and Isabella was entirely that of a deeply affectionate father and daughter, or of a doting uncle for his niece.’
Just guessing, which is that it was a political marriage to consolidate an alliance between countries or factions.
perhaps because Uncle Richard preferred men